57 research outputs found
Energy distribution and effective temperatures in a driven dissipative model
We investigate non-equilibrium behavior of driven dissipative systems, using
the model presented in [Phys. Rev. Lett. 93, 240601 (2004)]. We solve the
non-Boltzmann steady state energy distribution and the temporal evolution to
it, and find its high energy tail to behave exponentially. We demonstrate that
various measures of effective temperatures generally differ. We discuss
infinite hierarchies of effective temperatures defined from moments of the
non-exponential energy distribution, and relate them to the "configurational
temperature", measured directly from instantaneous particle locations without
any kinetic information. We calculate the "granular temperature",
characterizing the average energy in the system, two different "fluctuation
temperatures", scaling fluctuation-dissipation relations, and the "entropic
temperature", defined from differentiating the entropy with respect to energy
Jamming Mechanisms and Density Dependence in a Kinetically-Constrained Model
We add relaxation mechanisms that mimic the effect of temperature and
non-equilibrium driving to the recently-proposed spiral model which jams at a
critical density rho_c < 1. This enables us to explore unjamming by temperature
or driving at rho_c < rho < 1. We numerically calculate the relaxation time of
the persistence function and its spatial heterogeneity. We disentangle the
three different relaxation mechanisms responsible for unjamming when varying
density, temperature, and driving strength, respectively. We show that the
spatial scale of dynamic heterogeneity depends on density much more strongly
than on temperature and driving
Jamming Percolation in Three Dimensions
We introduce a three-dimensional model for jamming and glasses, and prove
that the fraction of frozen particles is discontinuous at the
directed-percolation critical density. In agreement with the accepted scenario
for jamming- and glass-transitions, this is a mixed-order transition; the
discontinuity is accompanied by diverging length- and time-scales. Because
one-dimensional directed-percolation paths comprise the backbone of frozen
particles, the unfrozen rattlers may use the third dimension to travel between
their cages. Thus the dynamics are diffusive on long-times even above the
critical density for jamming.Comment: 6 pages, 6 figure
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